Internet Explorer is no longer supported by Microsoft. To browse the NIHR site please use a modern, secure browser like Google Chrome, Mozilla Firefox, or Microsoft Edge.

New clinical trial to test treatment for mpox

Published: 23 August 2022

The team behind the world-leading RECOVERY trial of COVID-19 treatments are leading a new study investigating a potential treatment for people who have been diagnosed with mpox (previously known as monkeypox). The NIHR has commissioned and funded the study. The first patients have now been recruited.

Mpox, a member of the smallpox family of viruses, has historically been rare outside west and central Africa. However, in May this year, an outbreak was identified in the UK, followed by cases appearing in multiple other countries outside Africa. On 23 July this year, the World Health Organization declared mpox to be a Public Health Emergency of International Concern. Typical symptoms of mpox include a rash with painful blisters, which may be widespread or affect just one part of the body. Other symptoms can include fever, muscle ache, and swelling of lymph glands. Mpox usually gets better without treatment but this can take several weeks and, rarely, there may be serious complications.

Although vaccines developed for smallpox may reduce the risk of catching mpox, there are currently no proven therapeutics to speed recovery in those who develop the disease. The Placebo-controlled randomised trial of tecovirimat in non-hospitalised mpox patients (PLATINUM) study will test the efficacy and safety of tecovirimat, an antiviral treatment originally developed for smallpox.

Tecovirimat (also known as TPOXX®) prevents the virus from leaving infected cells, stopping its spread within the body. It was licensed earlier this year by the Medicines and Health products Regulatory Agency (MHRA) for mpox based on promising results from initial studies in animals and evidence of safety in healthy human volunteers. It is currently in use for the treatment of patients with severe complications of mpox who are admitted to hospital. However, to date there have been no clinical trials to confirm whether the drug can help mpox patients recover from the disease.

PLATINUM is being led by Sir Peter Horby, Professor of Emerging Infections and Global Health at the University of Oxford and the Director of the new Pandemic Sciences Institute, and Sir Martin Landray, Professor of Medicine & Epidemiology at Oxford Population Health, the joint chief investigators of the Randomised Evaluation of COVID-19 (RECOVERY) trial. The study also involves experts from the UK Health Security Agency, Chelsea and Westminster Hospital NHS Foundation Trust, and the University of Liverpool, who have experience in the clinical assessment and laboratory analysis of human mpox infections in the UK.

Professor Sir Peter Horby said: ‘Mpox is a distressing and sometimes dangerous infection. For the benefit of current and future patients worldwide who have been diagnosed with mpox, we need definitive evidence that tecovirimat is safe and effective. Although the early data on tecovirimat are promising, only a randomised clinical trial will provide the level of evidence we need to treat patients with confidence. PLATINUM will provide that evidence.’

Professor Lucy Chappell, Chief Executive of the NIHR and Chief Scientific Adviser at the Department of Health and Social Care said: ‘This study is a very important next step towards looking at treatments for mpox for those being outside of hospital. It’s crucial that we invest in developing, refining and evaluating treatments for this disease. We have commissioned this research to show the sense of and seriousness with which the health research community is collectively approaching this issue.

‘The trial will be run by a team including Sir Peter Horby’s preeminent RECOVERY team, whose world-leading work was so impactful for improving patient outcomes during throughout the COVID-19 pandemic. The rigour and robustness of this study will ensure that the findings are widely recognised, and help us to move forward in evaluating treatments for mpox.’

In PLATINUM, participants will be randomly allocated to receive either a 14-day course of 600 mg tecovirimat twice daily or a matched placebo treatment. Unlike RECOVERY, which recruited hospital patients, PLATINUM will be a community-based trial, with participants taking the treatment or placebo in their own homes. Eligible participants will be identified following clinical assessment and laboratory confirmation of mpox infection as part of usual NHS clinical care. The study aims to recruit at least 500 participants from across the UK.

To find out whether tecovirimat helps patients to recover faster, the study will assess the rate at which skin and mucosal lesions heal. It will also assess the time taken until throat and lesion swabs test negative for mpox virus and the proportion of patients who require hospitalisation due to complications from the disease.

Minister for Public Health, Maggie Throup said: ‘This government-funded study is an important step to finding a treatment which can help speed up the recovery of those who have mpox.

‘Led by the same experts behind the world-leading COVID-19 RECOVERY trial – which developed ground-breaking treatments for patients – this new mpox treatment trial will test the effectiveness of the antiviral tecovirimat in fighting the disease.

‘Vaccines remain our best defence against the spread of mpox – we urge all those eligible to come forward when contacted, and report any symptoms to NHS 111.’

PLATINUM is being funded by a £3.7 million award from the NIHR following an open call for proposals. Both tecovirimat and the placebo treatment are being provided by SIGA Technologies Inc.

Latest news